China has blocked internet access in parts of Urumqi – the capital of the northwestern Xinjiang province – after violent clashes between the minority Muslim Uighurs and Han Chinese reportedly left 156 dead and more than 1,000 injured.

“We cut Internet connection in some areas of Urumqi in order to quench the riot quickly and prevent violence from spreading to other places,” Li Zhi, Communist Party of China chief of Urumqi told the state-run media outlet Xinhua.

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He did not say when internet services would resume, but claimed Chinese authorities have evidence that Uyghur political activist Rebiya Kadeer was using the internet to “mastermind” the Sunday riot. The former millionaire businesswoman, now exiled to the US, has denied involvement in the riots and condemned the reported violent actions.

“These accusations are completely false. I did not organize the protests or call on people to demonstrate,” she said in a press conference in Washington on Monday.